The purpose of the proposed study is to investigate the factors involved in development of electrical hyperexcitability following chronic neural isolation of areas of cerebral cortex; to study the nature of generation, conduction and transmission of epileptiform afterdischarge and the factors modifying these in normal and hyperexcitable cortex; to attempt to correlate changes following neural isolation with changes in synaptic activity and to correlate these with mechanisms controlling cortical excitability; to study potential mechanisms for the action of anticonvulsant drugs, convulsant drugs and the changes in cortical excitability induced by withdrawal from anticonvulsant, sedative-hypnotic, and other drugs which share withdrawal hyperexcitability as a common feature. In addition: to continue to assess the hypothesis that denervation supersensitivity plays a role in the development of neurological and behavioral disorders following injury or chemically induced deprivation of input to areas within the central nervous system; and, to examine potential mechanisms which may explain the discrete nature of the changes occurring following injury to cerebral cortex.